The present invention relates to a rack and pinion power steering apparatus and, in particular, to a bushing assembly for a rack and pinion power steering apparatus.
A conventional hydraulic rack and pinion power steering apparatus for a vehicle includes a rack that extends axially through a chamber inside a hydraulic cylinder, or housing. The ends of the rack project axially outward from the terminal ends of the housing and are connected with steering linkages that connect to steerable vehicle wheels.
A piston is fixed to the rack within the chamber. Rotation of the vehicle steering wheel actuates a hydraulic valve and causes hydraulic fluid under pressure to act against the piston. The force exerted by the hydraulic fluid moves the piston within the chamber, causing the rack to move axially. The axial movement of the rack moves the steering linkage that, in turn, causes the steerable vehicle wheels to turn.
To prevent hydraulic fluid from flowing out of the chamber, it is necessary to seal the ends of the chamber through which the rack projects. It is also desirable to support the rack for axial movement within the chamber without losing the integrity of the seal. A bushing assembly is typically used for this purpose. Moreover, it is known to enclose the ends of the chamber with bellows attached to the housing to prevent the ingress of moisture, dirt, or other contaminants into the housing.
A bushing structure that enables the secure connection of the bushing to a plain, unmachined end of the housing, and to the bellows, with a minimal number of separate pieces would increase service life of the bushing apparatus while decreasing assembly time and production cost.
In accordance with one feature of the present invention, a fluid power assisted rack and pinion steering apparatus for a vehicle comprises a rack connectable with steerable wheels of the vehicle, a housing partially enclosing the rack and defining a fluid chamber, a bushing encircling the rack and having opposite axial ends, a sleeve supporting the rack for sliding movement relative to the bushing, and a fluid tight seal member for sealing the fluid chamber. The rack has a longitudinal axis and is movable in opposite axial directions to turn the steerable wheels in opposite directions. The bushing is secured in the housing by an interference fit between an outer surface of the bushing and an inner surface of the housing. The sleeve is located between the bushing and the rack and engages the rack. The sleeve has at least one radially extending tab received in at least one corresponding recess in the bushing. The at least one radially extending tab axially and rotationally locates the sleeve relative to the bushing.
In accordance with another feature of the present invention, a fluid power assisted rack and pinion steering apparatus for a vehicle comprises a rack connectable with steerable wheels of the vehicle, a housing partially enclosing the rack and defining a fluid chamber, a bushing encircling the rack, a sleeve supporting the rack for sliding movement relative to the bushing, and a fluid tight seal member for sealing the fluid chamber. The rack has a longitudinal axis and is movable in opposite axial directions to turn the steerable wheels in opposite directions. The housing has at least one terminal end portion with a cylindrical inner surface having a constant inner diameter. The bushing has an outer surface engaging the inner surface of the housing. The bushing has a first end portion and a second axially opposite second end portion. The sleeve has at least one radially extending tab for receipt in at least one corresponding recess at the second end portion of the bushing. The radially extending tab both axially and rotationally secures the sleeve to the bushing. The seal member is located in a recess at the first end portion of the bushing.